Generally, when video signals are recorded on a tape, control pulses are also recorded on a side of the tape to assure that the speed and phase during regeneration are the same as that of the recording process.
However, due to various reasons such as degradation of the tape, the control pulses on the tape become suppressed or unreadable, so frequently the speed and phase of the regeneration is different from those of the recording process due to the absence of the control pulses, thereby making it impossible to maintain a proper picture state. That is, if a tape in which no control pulse is detected is to be regenerated, noises occur on the pictures due to a hunting phenomenon, thereby degrading the picture.